PLASMA-CONCENTRATIONS OF PROGESTERONE DURING ESTROUS CYCLES OF ETHIOPIAN MENZ SHEEP USING ENZYME-IMMUNOASSAY

Plasma progesterone concentrations were assessed with a commercially available ELISA technique in 20 Ethiopian Menz ewes during their oestrous cycles which averaged 17.2 ± 1.0 (range 15-20) days (n=36). Average progesterone levels were significantly (P<0.0001) different between ewes (range 2.43-4.80 ng/ml) and days (P<0.0001) of their oestrous cycles (0.32-5.84 ng/ml). Progesterone values were under 1.0 ng/ml from 2 days before to 4 days after oestrus. Hormone concentration rose steadily to peak at 5.0-5.6 ng/ml on days 10 to 14. This was followed by a rapid decline to 3.0 ng/ml (53% of day 14 peak value) on day 15; 0.8 ng/ml (15% of peak value) on day 16; and 0.2 ng/ml (3.7%) on the day before oestrus. It is concluded that the ELISA method can be used for progesterone determination in Ethiopian sheep, and also, that progesterone levels of under 1.0 ng/ml are indicative of either anoestrous or the follicular and early luteal phases of the oestrous cycle. © 1990.